Hydrophones for recording underwater sound are known in the art. Such hydrophones are, for example, in the form of spheres having a diameter of 2 cm to 4 cm. The outer sphere surface includes a piezoelectric material that generates an electrical signal corresponding to the underwater sound by the piezoelectric effect upon impinging sound waves.
Also known are hydrophones having a planar sensor area, the physical effect of which is also based upon the piezoelectric effect.
For performing stereophonic acoustic underwater recordings, directivity of the applied hydrophones is desirable that is also present in an audible frequency range. Currently, however, there are no hydrophones available that provide a corresponding directivity in a range from 20 Hz to 20 kHz for facilitating stereophonic recordings. Moreover, the response characteristic of a conventional piezoelectric spherical hydrophone is too fast, so that acoustical sound recordings sound unfamiliar and distorted to the human ear.
Nevertheless, in order to facilitate stereophonic recordings, hydrophone configurations in the form of a chain or a matrix have been used up to now. The signals thus recorded are evaluated utilizing propagation time effects, which leads to the generation of comb filter effects due to phase shifts, which also has a negative influence on the sound perception.
In the case of underwater video recordings, it is desirable to improve the overall impression to accompany the underwater video recordings with recordings of stereophonic underwater sound in an audible frequency range and in an undistorted manner, i.e., with as little distortion as possible. However, the chain or matrix configurations of hydrophones usually have a size that underwater movement, e.g. by a diver conducting the underwater video recordings, is not possible.
There are military systems in use including a large number of sound converters. The signals recorded by the sound converters are electronically assembled to form one single signal. It is possible to alter the propagation times of the different signals. With this technology, it is possible to calculate one highly focused signal from the undirected individual signals using excessive computing power. It is disadvantageous that such systems demand a high implementation effort and require computing power.
It is a problem underlying the prior art to provide a hydrophone and a hydrophone assembly by which it is possible to perform stereophonic underwater sound recordings in a frequency range from 1 kHz to 30 kHz, in particular, in an audible frequency range, with very low distortion.
Thus, a need exists to overcome the problems with the prior art systems, designs, and processes as discussed above.